Conversion of coal to liquid products



June` 30, 1970 N. J. PATr-:RsoN

CONVERSION OF COAL T0 LIQUID PRODUCTS Filed March 29, 1968 2 Sheets-Sheet 1 June 30, 1970 N. J. PATERsoN CONVERSION OF COAL TO LIQUID PRODUCTS 2 Sheets-Shea?. 2

Filed March 29, 1968` WEIGHT PERCENT EXTRACT OBTAINED FROM mGF UTAH COAL FIG.2

INV ENTOR NORMA/v J. PA TERso/v United States Patent O U.S. Cl. 208-50 5 Claims ABSTRACT OF THE DISCLOSURE This disclosure relates to a process for converting coal primarily to motor fuels by a process combination wherein (a) coal particles are mixed with solvent, such as a gas oil boiling between about 300 and 750 F.; (b) the m-ixture of coal particles and solvent is hydrovisbroken and hydrocarbons are extracted from the coal by passing the mixture through a heated coil together with H2 and H2O; (c) the hydrovisbreaker coil effluent is fractionated into several cuts; and (d) these several cuts are selectively subjected to hydrogenation and coking as interconnected processing steps to obtain a high yield of motor fuel with relatively low hydrogen consumption per ton of coal.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a process for the conversion of solid carbonaceous materials primarily to liquid hydrocarbon products. More particularly, this invention relates to a combination process for the production of hydrogen-enriched products such as gasoline from materials such as coal.

Definitions Motor fuels.-Normally liquid hydrocarbons used to supply the energy upon burning to drive an automobile motor, an airplane motor, a jet airplane motor, or any other motor.

Gas ol.-The term gas oil is used to refer to a variety of hydrocarbon fractions boiling generally between about 300 F. and 1,200 F. For purposes of this specification, gas oils include fractions, such as 300 to 750 F. boiling range, as well as more narrow fractions, such as 400 to 600 F., 350 to 550 F., etc. Most generally, gas oils boiling between 300 F. and about 750 F. are referred to simply as gas oils. Gas oils boiling in excess of 750 F. are often referred to as heavy gas oils, as for example a gas oil boiling between 750 and 1,050 F. Again, a variety of boiling ranges are meant to be included by the term heavy gas oil, such as 600 to 900 F., 650 to 850 F., 800 to 1,100 F., etc.

Boiling range- The temperatures at atmospheric pressure at which initial vaporization is obtained and iinal vaporization is obtained, respectively, according to standard ASTM tests. In the case of heavy fractions, the boiling temperature is corrected to atmospheric pressure after vacuum distillation. In many instances, the exact initial or iinal boiling point is not determined b-ut is instead approximated. Also, because a large number of hydrocarbons having only slightly diiferent boiling points make up any given fraction, it is to be understood that in this specification boiling points are not exact but are used to describe a cut in general. For example, a 300 F. cut may have a boiling range of 160 to 310 P. or to 305 F. etc.

Pitch.-A mixture comprised of coal ash and high boiling range hydrocarbons including tars and asphalt.

3,518,182 Patented June 30, 1970 Description of the prior art Coal is an ash containing hydrogen-deficient, hydrocarbonaceous solid. By ash is meant metallic contaminants and the compounds of silica that are present in coal. The most serious disadvantage of coal with regard to the production of liquid fuels therefrom is the Very low hydrogen content of coal. The hydrogen to carbon ratio of a representative Pittsburgh seam bituminous coal is about .06 to .07, while the hydrogen to carbon ratio of a conventional gasoline is about .14 to .18. Therefore, in any process for the production of liquid fuels from coal, it is necessary to raise the hydrogen to carbon ratio of coal either by the direct addition of hydrogen or by the rejection of carbon or a combination of both.

Three processes to produce liquid fuels from coal have obtained sufficient commercial `feasibility to nd application abroad. The oldest process is the hydrogenation process developed by Berguis. In the Berguis process, substantially all the coal is liquefied via catalytic hydrogenation in the presence of a hydrocarbon diluent and hydrogen under pressures of 3,000 p.s.i.g. or higher. The effluent hydrogenation product is subsequently treated with additional hydrogen to yield liquid fuels. A second process which has been developed is the Fischer-Tropsch process wherein essentially all of the coal is gasified via reaction with steam and oxygen.. A raw synthesis gas comprised of hydrogen and CO is obtained by the gasification of the coal. The hydrogen and CO are reacted in the presence of an iron or cobalt catalyst to yield liquid hydrocarbons and water, A third process is the Pott- Broche process wherein substantially all of the coal is liquefied via solvent extraction under pressure. The resulting coal extract is subsequently catalytically hydrogenated to yield liquid fuels.

None of the above processing routes have been found economically attractive for application in the United States. Also, in spite of the enormous deposits of coal in the United States to date, no new process for converting coal to motor fuels has been developed that appears to have suicient economic attractiveness `for commercial application in the U.S.

Many of the processes suggested according to the prior art are directed to the conversion of a large part of the coal into an intermediate product, such as an extract, which by subsequent hydrogenation is sought to be largely converted into gasoline and other liquid hydrocarbon products. In cases where coal can. be converted substantially into an extract, the resulting extract is nearly as difficult to hydrogenate to gasoline and similar light products as the original coal. Such a conversion is economically unattractive due to the consumption of large quantities of hydrogen and the high cost of the hydrogen.

The extraction of hydrocarbons from coal by means of solvents has been widely proposed. In some instances, extraction has been accompanied by concurrent hydrogenation. In other cases, the hydrogen-decient fraction of the coal has been rejected as by the deposition and separation of coke. The ditlculty with such concurrent addition of hydrogen or concurrent rejection of carbon is that both are relatively nonselective since the total extract is subjected to such treatment as well as the coal residue. Thus uncontrolled and inefficient distribution of hydrogen is effected.

According to many of the processes proposed by the prior art for theextraction of liquid products from coal, the mixture of coal and extract is separated by filtration either before or after partial hydrogenation. This ltration step has resulted in a great number of problems in carrying out the conversion of coal to liquid products. In particular, the filters frequently are blinded, that is, plugged by the ash material from the coal. Also, corrosion problems are incurred, and ash removal is incomplete. Ash which is present in the coal-extractant mixture 1s alkaline and will poison catalysts used to effect hydrogenation concurrently with the extraction step. Also, if the hydrocarbons extracted from the coal are hydrogenated as a group, the problem of substantial catalyst deactivation is encountered even if only a very small amount of ash is present in the oil feed to catalytic hydrogenation.

SUMMARY OF THE INVENTION According to the present invention, a process is provided for converting coal to motor fuels which comprises the following steps in combination: (a) mixing coal particles with a solvent comprised of a gas oil to obtain a coal-gas oil slurry; (b) hydrovisbreaking the coal-gas oil slurry by passing the coal-gas oil slurry through a heated tubular coil together with H2 and H2O under the following conditions: (l) 100 to 1,000 s.c.f. of H2 per barrel of slurry; (2) 0.1 to 5.0 weight percent H2O based on slurry weight; (3) coil outlet temperature between 60G-900 F.; (4) residence time in the coil between 10 and 500 seconds, whereby there is obtained a hydrovisbreaker eiuent; (c) distilling the hydrovisbreaker effluent to obtain a first gas oil, a heavy gas oil, and a pitch; (d) reacting the heavy gas oil and a first heavy bottoms oil obtained as hereinbelow described with hydrogen under catalytic hydrogenation conditions in a hydroconversion zone to obtain hydrogen-enriched oil and distilling the hydrogen-enriched oil to obtain a second gas oil and a second heavy bottoms oil; (e) coking the pitch and the second heavy bottoms oil in a coking unit to obtain coke and coker vapors and distilling the coker vapors to obtain a third gas oil and the first heavy bottoms oil; and (f) converting at least a substantial portion (i.e., between 50 and 100 percent) of the first, second and third gas oils to motor fuels by catalyzed reaction of the gas oils with hydrogen at elevated temperature and pressure.

Preferably the gas oil used as a solvent in the present invention boils in the range 300 to 750 F. and is generated by one or more of the process steps of the present process combination. For example, the gas oil solvent may be a portion of the first, the second, or the third gas oil or mixtures thereof.

In carrying out the process of the present invention, hydrogen is chemically combined with the liquid material extracted from the coal in a selective and controlled manner. Only a nominal amount of hydrogen, that is, between 100 and 700 standard cubic feet of hydrogen per barrel of slurry, preferably about 300-500 standard cubic feet of hydrogen, is added to the coal solvent slurry in the hydrovisbreaking step of the present invention. Of this hydrogen, preferably only about 300 standard cubic feet per barrel of slurry is chemically combined with the slurry.

Thus there is only a relatively small amount of hydrogenation effected in the hydrovisbreaker coil. The hydrogen that is added to the slurry feed to the hydrovisbreaker coil serves primarily to aid in extracting heavy hydrocarbons from the coal particles and to aid in preventing coke formation in the coil.

The bulk of the hydrogenation of the coal-derived hydrocarbons is effected after the hydrovisbreakingextraction step. Thus heavy gas oil is separated from the hydrovisbreaker eiuent and is hydrogen enriched by catalytic hydrogenation. A pitch stream is separated from the hydrovisbreaker eiuent, and the very heaviest, the most refractory and ash material is separated from the pitch by coking. The coking thus serves to reject material that is very hydrogen deficient. However, to aid in obtaining high yields of hydrocarbon material, the coking is preferably carried out in the presence of hydrogen-donor gas oil. The hydrogen-donor gas oil which is preferably used is part of the eifluent material from catalytic hydrogenation of the hydrovisbreaker efuent heavy gas oil. This gas oil is heated to between 950 and 1,200 F., preferably about 1,050-1,100 F., in a furnace so that the gas oil is sufficiently hot to serve as the heating medium for the coking step. The hot hydrogen-donor gas oil also serves advantageously to extract, from the pitch, hydrocarbons which are quite difficult to extract. The gas oil used in the coking step may be comprised of portions of the other gas oils generated in the process according to the present invention, but preferably at least part of the gas oil is hydrogen enriched as is the gas oil obtained from catalytic hydrogenation.

According to a preferred embodiment of the present invention, the coking unit is a delayed coker comprised of two or more coking drums.

In the ypresent invention, there is no filtration step. The heavy pitch which is obtained by vacuum distillation after the hydrovisbreaking step of the present invention is passed to a coking unit. Thus ash contained in the coal, which ash accompanies the pitch, is removed with the solid coke from the delayed coking drums. The coke is advantageously partially oxidized to form hydrogen used in the process combination of the present invention. The ash is withdrawn from the partial oxidation plant, possibly together with catalyst fines, and many be used as an ingredient in building cements or may be passed to metals recovery.

It is an important feature of the present invention that the hydrovisbreaker effluent is distilled to obtain a relatively ash-free oil and an ash-rich pitch which is used as Coker feed. The ash-rich pitch is processed by coking so as to obtain hydrocarbons from the pitch and separate hydrogen-deficient material and ash in the form of coke.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a schematic process flow diagram of the basic processing steps according to the present invention.

In FIG. 2, weight per-cent extraction is plotted versus viscosity of the 300 F. plus portion of the ellluent from the hydrovisbreaker. The curve in FIG. 2 connecting the plotted points shows how increased hydrovisbreaker severity (as reflected by weight percent extraction) affects the viscosity of the 300 F. plus portion of the eiiiuent from the hydrovisbreaker.

DETAILED DESCRIPTION OF THE DRAWINGS Referring now in more detail to the drawings, in FIG. 1 coal particles and solvent circulated via line 15 are mixed together in slurry tank 2. Typical coals used in the process of t-he present invention contain 20 to 50` weight percent volatiles, 70 to 85 weight percent carbon, and 2 to 15 weight percent ash. If the moisture content of the coal is between 1 and 3 weight percent, then no drying is required. However, if the moisture content of the coal is excessive, say 5 tolO weight percent, then it is desirable to dry the coal previous to introducing the coal into the slurry tank. The coal is preferably bituminous coal which has been freshly mined to thus avoid oxidation by prolonged exposure to air. The coal, which is fed t0 'the slurry tank in line 1, is of a particle size less than about 1t-inch in diameter or length. In the process ofthe present invention, it is not required to grind the coal into very fine particles, such as /200 mesh, because in the hydrovisbreaking-extracting step of the present invention the coal rapidly disintegrates due to the action of the solvent gas oil and the turbulent conditions existing in the hydrovisbreaker coil. Although in this specification, for simplicity, the hydrovisbreaking-extraction zone 7 is generally referred to as a hydrovisbreaker, it is to be understood that in addition to reduction of viscosity of the liquid portion of the slurry feed, the hydrovisbreaker serves the important function of extracting hydrocarbons from the coal in the slurry.

Temperature in the slurry tank is maintained at about 225 to 275 F. lby preheating the solvent and/or steam jacketing the slurry tank. It is advantageous to continuously agitate the coal and extractant mixture in the slurry tank by the introduction of an oxygen-free inert gas in addition to mechanical mixing of the contents of the slurry tank.

Hydrovsbreaking extracting zone The slurry of coal and solvent is withdrawn from the slurry tank in line 5 and is passed together with water or steam introduced in line 5 and hydrogen introduced in line 6 to coil 8. Coil 8 is located in a furnace so that the coil and its contents may be heated to high temperatures. In the ypresent invention, gas oils are the preferred solvents for the extraction of hydrocarbons from the coal. According to the present invention, the solvent is generated from one or more of the several processing steps in the overall processing scheme. Accordingly, the composition of the solvent will vary somewhat with the type of coal being processed, the extraction conditions, and the particular processing steps from which the solvent is derived. However, the preferred solvent for use in the process of the present invention boils in the range 300 to 750 F. and is composed of a mixture of aromatics and naphthenes comprised of dialkylbenzenes, naphthalenes, anthracene, alpha-methylnaphthalene, alpha-naphthylamine, phenanthrene, Tetralin, alpha-methylphenanthrene, fluorence, 9,l-di-hydrophenathrene, 1-methylisopropylphenanthrene, and naphthene.

The slurry of coal and extractant is passed at high velocity together with 100 to 1,000 standard cubic feet of hydrogen per barrel of slurry and 0.1 to 5.0 weight percent H2O through tubular coil 8. The presence of H2O, which is mostly steam at the temperatures existing in the coil, serves to increase the velocity of the stream flowing through the coil and also to increase the turbulence of the stream flowing through the coil. The termperature at the inlet of the coil is about 200 to 300 F., and the outlet of the coil is generally maintained in the range 600 to 900 F., preferably 700 to 825 F. Inlet pressure for the coil is preferably maintained in the range 1,000 to 1,200 p.s.i.g.; and outlet pressure from 200 to 300 P Turbulent flow in the coil is critical for the intimate contacting of the coal and the extractant. To achieve this purpose, Reynolds numbers of 2,500 to 11,000, preferably 5,000 to 10,000, are maintained for the slurry flowing through the coil. Residence time in the coil is in the range of 10 seconds to 500 seconds, preferably 10 seconds to 90 seconds. Due to the high velocities, turbulence, and the erosive nature of the slurry, streamline return bends are preferred for the coil.

In the hydrovisbreaking extracting operation, there is a well-deiined relationship between the yield of extract and the viscosity in centistokes at a given temperature of 300 F .-lmaterial in the furnace etlluent. Thus referring to FIG. 2, there is shown the viscosity of 300 F.| hydrovisbreaker effluent versus weight percent extraction. FIG. 2 is for a particular representative coal, which is Utah bituminous coal. However, a similar Uashape curve is obtained for other coals. Thus, although FIG. 2 is calculated for a mixture of 40 percent `by Weight Utah coal and 60 percent by weight gas oil solvent having an initial viscosity of 14 centistokes at 210 F., a series of curves may be derived for viscosity versus weight percent extract for varying weight percents of coal to solvent and for dilferent types of coal. FIG. 2 shows that the viscosity of the 300 F.l slurry at first rises slowly as material is extracted from the coal and then begins to fall towards the minimum. The amount of material extracted from the coal is a function of the severity in the hydrovisbreaker. The severity may be increased by increasing the temperature in the coil, particularly the coil outlet temperature, or by increasing the residence time of the slurry in the coil. It is preferable to maintain the severity in the hydrovisbreaking step of the present invention at or about the minimum viscosity for the 300 F.} eiuent from the hydrovisbreaker coil as illustrated by point M in FIG. 2. The severity may be increased beyond the minimum viscosity to obtain higher yields of extract; but this will result in increased viscosity, indicating that polymerization reactions are causing the formation of heavy material, which is undesirable where motor fuel production is one of the primary goals. Generally the weight percent extraction after passage through the hydrovisbreaker coil is 60 to 90 percent based on m.a.f. coal fed to the process in line 1, `but the amount of extraction is Varied within this range so that the viscosity of the extract and solvent eflluent from the coilis approximately minimized.

Referring again to FIG. 1, the addition of hydrogen in line 6 to the slurry fed to tubular coil I8 serves to permit longer sustained operation of the hydrovisbreaker by inhibiting the formation of olenic coke precursors. Also, with respect to the extraction effected in the hydrovisbreaker, the added hydrogen serves to aid in the dissolving of the coal in the solvent. Thus the presence of hydrogen tends to speed up the initial dissolving of the coal and serves to enhance depolymerization which is effected under the conditions maintained in the hydrovisbreaker.

Distillation zone 10 The material from tubular coil 8 is passed in line 9 to distillation zone 10. Distillation zone 10 may suitably be comprised of three distillation columns. The first distillation column serves to separate hydrogen, CO2, H28, NH3 and light hydrocarbons, such as methane through butane, from the heavier material in the hydrovisbreaker effluent. This rst distillation column is preferably operated at a pressure of from 50 to 100 p.s.i.g. The light gases obtained as overhead in this rst distillation column are passed to gas recovery processing. The heavier material is with` drawn from the lower part of the first distillation column and passed to a second distillation column operating at 20 to 50 p.s.i.g. A hydrocarbon cut boiling in the range pentane I(C5) to 300 F. is withdrawn from the overhead of the second distillation column and then passed, as indicated by lines 12 and 60 in FIG. 1, to hydroconversion zone 65. Material heavier than a normal boiling point of 300 F. is withdrawn from the lower part of the second distillation column and passed to a vacuum distillation column. From the upper part of the vacuum distillation column a gas oil, preferably 'boiling in the range 300 to 750 F., is withdrawn as indicated by line 13 from distillation zone 10. This gas oil is combined with gas oil from distillation zone 50 and/or 35. A portion of the combined gas oil is preferably recycled via line 15 for use as a solvent in slurry tank 2. y

As an intermediate fraction or cut from the vacuum distillation column, a heavy gas oil is withdrawn. Preferably the heavy gas oil boils over the range 750 to 1,050 F. However, since the heavy gas oil is next passed via lines 14 and 28 to hydroconversion zone 29 for reaction with hydrogen in the presence of the catalyst, in some cases it is preferable to lower the upper cut point to 1,000 F. or 900 F. to insure low ash and metals content in the heavy gas oil. As previously indicated, small amounts of ash will reduce the activity of the hydroconversion catalyst. Thus it is necessary to design and operate the vacuum distillation column so that there is only a small amount of ash and/or metallic contaminants in the heavy gas oil. The` ash contaminants in the heavy gas oil should be no more than p.p.m. lby weight as metals, preferably less than 10 p.p.m., and still more preferably less than 3 p.p.m. By careful design of the vacuum distillation column so as to minimize entrainment of pitch into the heavy gas oil (e.g., by providing ample cross-sectional ow area at the ash zone), the above low ash contents may be achieved without excessive expense for heavy gas oil cuts boiling as high as 1,050 F.

From the bottom of the vacuum column in distillation zone 10, a pitch stream is withdrawn n line 39. This pitch is derived from the coal feed and contains ash, heavy hydrogen-deficient carbonaceous material, and some very difficult to extract nonhydrogen-decient hydrocarbons.

Hydroconversion zone 29 Hydroconversion zone 29 is preferably composed of a single-stage, once-through hydrocracker. Preferred catalysts are nickel-molybdenum or nickel-tungsten on an alumina-silica base. Suitable temperatures are 600-900 F., and preferred temperatures are 7'25 to 825 F. Suitable pressures are 1,500 to 5,000 p.s.i.g., and preferred pressures are 2,500 to 3,500 p.s.i.g. Suitable liquid hourly space velocities (LHSV) are 0.1 to 10.0, and Preferred LHSVs are 0.3 to 1.3. Suitable hydrogen recycle rates are LOGO-15,000 s.c.f. per barrel of oil feed. Suitable fresh hydrogen rates to replenish chemically consumed hydrogen are LOGO-2,000 s.c.f. per barrel of oil feed.

As shown in FIG. 1, preferably a 750-1,050 F. heavy gas oil cut is withdrawn from distillation zone 10 in line 14 and passed to hydroconversion zone 29 together with a heavy bottoms Stream that is 750 F.-{ boiling range hydrocarbons obtained from distillation zone 50. The 750 to 1,050 F. cut from distillation zone 10, which may be referred to more generally as a heavy gas oil cut, and the 750 F.+ bottoms Withdrawn from distillation zone 50, which may rbe referred to as a heavy bottoms oil, are converted by hydrocracking, preferably to the extent of 25 to 35 volume percent material boiling below 750 F. Also, the material fed to hydroconversion zone 29 is enriched in hydrogen content by catalytic hydrogenation of cracked (i.e, severed) hydrocarbon molecules as well as catalytic hydrogenation of uncracked hydrocarbon molecules (ie, molecules wherein nitrogen or sulfur is removed without cracking and molecules Iwherein unsaturated bonds are saturated without cracking). The hydrogen-enriched hydrocarbons obtained from hydroconversion zone 29 'boiling in the gas oil and in the heavy gas oil and above ranges are advantageously used as hydrogen donors in the coking step of the present invention.

The eluent from the hydrocracker reactor of hydroconversion zone 29, after separation of recycle hydrogen and -light hydrocarbons, is withdrawn in line 30 and passed to distillation zone 35. In distillation zone 35, the C-300 F. cut is separated and withdrawn in line 36 and passed, for example, to hydroconversion zone 65. The gas oil cut, preferably Iboiling 'between 300 and 750 F., is withdrawn in line 37, and at least a portion of this gas oil s preferably used as a hydrogen donor and heating medium in the coking step of the present process. A heavy bottoms oil, preferably -boiling from 750 F. upwards, is withdrawn from distillation zone 35 in line 38 for processing in the coking unit.

Delayed coking drums 42 Although other means, such as fluid coking, may be employed, it is preferable that a delayed coker comprised of two or more coking drums be used to effect the coking step of the present invention. The feed to the delayed coking drums is comprised of the pitch in line 39 from distillation zone and the 750 R+ boiling range hydrocarbons in line 38 from distillation zone 35. These streams are combined and passed in line 40 to circulating loop 41. Preferably, the heat for the coking operation is supplied by heating n heater 26 and then circulating to the coking unit a portion of the gas oil obtained from distillation zones 10, 35 and/or 50. Most preferably, the gas oil used as the heating medium for delayed coking is comprised of at least a portion of the hydrogen-enriched gas oil derived from hydroconversion zone 29. The gas oil heating medium is charged to heater 26 via line 25, withdrawn in line 27 at about 1,050 to 1,l50 F., and passed to circulating loop 41. Either valve 31 or 32 is open depending upon which of the relayed coking drums is in current operation. The heated material is introduced into the onstream coking drum at a temperature prefer- 8 ably between 900-950 F. Suicient heating medium gas oil is used to heat the pitch from about 400-700 F. and the 750 F.-imaterial in line 38 from about 30G-600 F. to the preferred temperature range of o-950 F. for the mixture. SuHicient residence time is available in the coking drum so that coke is formed. In accordance with procedures known in the art, the delayed coking drums are operated on a cycle of 18-30 hours, preferably about 24 hours. Vapors are continuously passed from the top of the onstream coking drum to distillation zone 50, and the level of the coke gradually builds up inthe coke drum. The coke contains ash from the original coal fed to the process in line 1. The coke is removed from the bottom of the coking drums via lines 43 and 44. Preferably, at least part of the coke is partially oxidized to form hydrogen for use in the present process. Thermal decomposition of part of the pitch and heavy gas oils during the coking operation results in the formation of lighter hydrocarbons. These hydrocarbons are withdrawn as vapor from the top of the onstream coke drum at a pressure of l0100 p.s.i.g. and temperature of S25-870 F. The gas oil heating medium, which is introduced to the circulating loop at a pressure of 500-750 p.s.i.g., also leaves the top of the coke drum as a vapor. The gas oil, in addition to serving as a heating medium and hydrogen donor, serves to sweep oil occluded in the coke into the vapor overhead stream from the coke drum. Also, the gas oil itself is 'beneficiated in the coke drum by the coking out of coke precursors contained in the gas oil.

Thus vaporous hydrocarbons are withdrawn overhead from the coker in line 45 and passed to distillation zone 50. In distillation zone 50, the vapors from the coking unit are separated into a C5-300" F. fraction in line 51 which is combined with the other C5-300 F. boiling range hydrocarbons and passed to hydroconversion zone 65 via line 60. A 30C-750 F. fraction is withdrawn in line 52, and a 750 F. fraction is withdrawn in line 53.

Hydroconversion zone 56 Within the concept of the present invention, the purpose of hydroconversion zone 56 is to convert at least a substantial portion of the gas oil material-eg., the material boiling between 30G-750 F.-to motor fuels by catalyzed reaction ol.' the -gas oil with hydrogen at elevated temperature `and pressure. Hydroconversion zone 56 preferably consists of a hydrotreating unit followed by a hydrocracking unit. Thus in a preferred embodiment of the present invention, a portion of the `gas oil from distillation zones 10, 35 and/or 50 is passed via line 55 to a hydrotreating unit. Suitable operating conditions for the hydrotreating reactor are:

Temperature-400-750 H2 partial pressure-1,750-2,500 p.s.i.g.

Liquid hourly space Velocity-0.54.5 Catalyst-Ni-Mo on alumina H2 recycle rate-1,000-l5,000 s.c.f./bbl.

Fresh H2 rate-l,000-3,500 s.c.f./bbl. of gas oil feed The eluent from the hydrotreater reactor is cooled, recycle H2 and light gases are separated from the heavier hydrocarbons, and the heavier hydrocarbons are passed to a hydrocracking unit.

Suitable operating conditions in the hydrocracking reactor are:

Temperature-SOO-SOO" F.

H2 partial pressure-l,200-l,800 p.s.i.g. Liquid hourly space velocity-0.54.5 Catalyst-Ni on silica-alumina H2 recycle rate-l,00015,000 s.c.f./bbl. Fresh H2 rate--SOO-LOOO s.c.f./ bbl.

The effluent from the hydrocracker reactor is cooled, H2 is separated for recycle, and light hydrocarbons are separated for recovery in a gas plant. The heavier hydrocarbons remaining are separated into a motor fuel cut boiling between C and 380 F. and a 380 F.+ cut. The 380 F.+ cut is preferably recycled to the hydrocracking unit. The motor fuel cut (C5-380 F.) may be withdrawn as product motor fuel via lines 57, 58 and 59; but, preferably, it is further separated into a fraction boiling between C54180 F. which is withdrawn in line 62 and a fraction boiling between 180-380 F. The fraction boiling between 180 F .-380 F. is passed via lines 61 and 67 to catalytic reforming zone 68. Feed to catalytic reforming zone 68 is preferably augmented by material boiling above 180 F. obtained from hydroconversion zone 65 via lines 66 and 67.

Hydroconversion zone 65 Feed introduced to hydroconversion zone 65 via line 60 is comprised of `C5-3O0" F. boiling range hydrocarbons in line 12 from distillation zone 10, C5-300 F. boiling range hydrocarbons in line 36 from distillation zone 35, and C5`-3O0 F. boiling range hydrocarbons in line 51 from distillation zone 50. Preferably, hydroconversion zone 65 is comprised of a single-stage hydrotreater. Suitable operating conditions in -the hydrotreater reactor are:

H2 partial pressure-l,0O0-2,250 p.s.i.g.

Liquid hourly space velocity-0.5-2.5 Catalyst-N-Mo on alumina H2 recycle rate-1,000-15,000 s.c.f./ bbl. of oil feed Fresh H2 rate-300-800 s.c.f./bbl. of oil feed The efliuent from the hydrotreater is cooled, recycle H2 is separated, light gases are separated and passed to a gas plant, and a C5-300" F. fraction separated. The C5-300 F. fraction may be passed entirely via line 62 to line 59 and withdrawn as product motor fuel. However, it is preferable to separate the C5-300 F. fraction into a cut boiling below 180 F., which is Withdrawn via line 62, and a 180 F.-300 F. cut which is passed via lines 66 and67 to catalytic reforming zone 68.

Alternatively, the 180-300" F. cut may be solvent eX- tracted to remove aromatics and the rainate passed to catalytic reforming zone 68. The aromatics, benzene, toluene, xylenes, etc., may be included in the motor gasoline or separated as petrochemical feedstocks.

Catalytic reforming zone 68 Thus feed to catalytic reforming zone 68 preferably is comprised of 180 F.-300 F. hydrocarbons from hydroconversion zone 65 and 180 F.-380 F. hydrocarbons from hydroconversion zone 56. Suitable operating conditions for the catalytic reforming reactor are:

The catalytic reforming serves to upgrade the octane rating of the feed hydrocarbons primarily by the dehydrogenation of naphthenes. The effluent from the catalytic reforming reactor, after separation of recycle H2 and light gases which are sent to a gas recovery plant, is withdrawn in line 69. The reformate in line 69 is combined with hydroconversion zone 65 eiuent in line 62 and hydroconversion zone 56 effluent in line 58 to thus obtain the product motor fuel `withdrawn from the process inline 59.

Example This example summarizes a calculated material balance for the integrated coal conversion process according to the present invention. In this example, the feed is 1,000 tons per day of Utah, Green Creek Bituminous Coal. The 1,000 tons is on a moisture and ash-free (maf.) basis.

( 1) Coal feed and preparation (a) Ultimate analysis of 1,000 tons of dried coal:

Carbon 1,605,000 Hydrogen 114,000 Oxygen 144,200 Sulfur 104,200 Nitrogen 32,600

Ash 160,800

Total coal feed 2,160,800

(b) 9,660 b.p.d. of 30G-750 F. solvent gas oil for a total of 3,241,200 lb./ day is added to the slurry tank.

(c) Thus the total feed to slurry tank is 5,402,000 lb./day.

(2) Hydrovisbreaker Net input Net dried coal 2, 160, B00 Water 54 D Reacted hydrogen Total 2, 234, B00

(3) Hydroconversion zone 29 Once-through, single-stage conventional hydrocracking 0f heavy gas oil U50-1,050 F. boiling range) from distillation zone 10 and heavy bottoms oil (750 R+) from distillation zone 50.

Input Lb./day API B.p.d.

Heavy gas oil (750-1,050 F.) 402, 000 1.0 1, 075 Heavy bottoms oil (750 F.+) 77, 040 3. 0 200 Total 479,040 0 4 1, 275 Net H2 (consumed) 0 Reactor input 495, 910

Product output Methane Ethane.. Propane.

Butanes.

1 1 (4) Delayed coking Feed input (net) Lb./day

(5) Hydroconversion zone 56 Conventional hydrotreating (1st stage) followed by hydrocracking (2nd stage) 30G-750 F. boiling range gas oil to obtain motor fuel. 3 5

Feed input Lb./day oAPI B.p.d. 40

From cokcr 47, 970 147 From hydrovisbreakcr 835, 785 12. 5 2, 430 From single-stage hydrocrackcr. 247, 955 23.0 774 Total 3, 351 Total hydrogen reacted stages 93, 554 45 Total input 1, 225, 264

Product output H2S NHg Methane Ethanc. Propane. Isobutane n-Butane C5, 180 F". R30-380 F Total 1, 225, 264 4,105

(6) Catalytic reforming (8) Overall process products Wt. percent based on B.p.d. Lb./day maf. coal Cl-Cz gas EFO 210 56, 525 2. 8 C3 375 66, 580 3. 3 C4 780 156, 435 7. 8 Coke- 1 91, 298 l 5. 5 Ash 160, 800 8.0 Ammoni 25, 800 1. 2 Hydrogen sulfde 110, 710 5. 5 Water 175, 705 7. 8 100 F-l -l- 3 cc. TEL motor fuel-.. 4, 535 l, 161, 867 58. 1

Total 2, 005, 000 -100. 0

lNet coke after meeting hydro en reqiiirernents. Part of the coke is consumed in a partial oxidation p ant for productlon of hydrogen for use in hydroconversion zones 56 and 65.

(9) Summary Yield of motor fuel per ton of moisture and ash-free (maf.) coal=4.5 bbl/ton.

Hydrogen consumption Total hydrogen. consumption per barrel of motor fuel=5,450 s.c.f.

The yield of 4.5 bbl. of motor fuel per ton of m.a.f. Utah bituminous coal with a hydrogen consumption per barrel of motor fuel of 5,450 s.c.f. illustrates the high efficiency and selectivity in hydrogen utilization while using the process of the present invention. After adding 3.0 cubic centimeters of tetraethyllead per barrel of motor fuel, the motor fuel has an octane rating of 100 F-l. Previously proposed processes for conversion of coal to motor fuels are stated to yield 3.0-3.5 bbl. of F-l (with 3 cc. tel. per bbl.) motor fuel per ton of coal with a hydrogen consumption of 6,000 s.c.f. per barrel of motor fuel produced.

Although various specific embodiments of the invention have been desecribed al1/1 shown, it is to be understood that they are meant to be illustrative only and not limiting. Certain features may be changed without departing from the spirit or essence of the invention. Accordingly, t-he invention is not to be construed as limited to the specific embodiments illustrated but only a defined in the following claims.

I claim:

1. Process for converting coal to motor fuel which comprises the following steps in combination:

(a) mixing coal particles with a solvent comprised of a gas oil to obtain a coal-gas oil slurry;

(b) hydrovisbreaking said coal-gas oil slurry by passing said coal-gas oil slurry through a heated tubular coil together with H2 and H2O under the following conditions:

(l) 100 to 1,000 s.c.f. of H2 per barrel of slurry; (2) 0.1 to 5.0 weight percent H2O based on slurry weight; (3) coil outlet temperature between 60G-900 F.; (4) residence time of the slurry in the coil between 10 and 500 seconds; whereby there is obtained a hydrovisbreaker effluent;

(c) distilling said hydrovisbreaker effluent to obtain a rst gas oil, a heavy gas oil, and a pitch;

(d) reacting said heavy gas oil and a rst heavy bottoms oil obtained as hereinbelow described with hydrogen under catalytic hydrogenation conditions in a hydroconversion zone to obtain hydrogen-enriched oil and distilling said hydrogen-enriched oil tolobtain a second gas oil and a second heavy bottoms o1 (e) coking said pitch and said second heavy bottoms oil in a coking unit to obtain coke and coker vapors and distilling the Coker vapors to obtain a third gas oil and said first heavy bottoms oil; and

(f) converting at least a substantial portion of the first, second and third gas oils to motor fuels by catalyzed reaction of said gas oils with hydrogen at elevated temperature and pressure.

2. Process according to claim 1 wherein said solvent is a portion of a gas oil selected from the group consist ing of said irst, said second, and said third gas oil or mixtures thereof.

3. `Process according to claim 1 wherein there is maintained a sufficiently high temperature and a sufficiently long residence time for the slurry in the coil to obtain a yield of extract from the coal between 60 and 90 weight percent based on moisture and ash-free coal, and wherein the viscosity of that portion of the hydrovisbreaker effluent normally boiling above 300 F. is approximately minimized.

4. Process according to claim 1 wherein the coking unit consists of at least two delayed coking drums and heat required to effect the coking is obtained by heating gas oil to a temperature between 1,050 and 1,150 F. and then combining the gas oil with the pitch and second heavy bottom oil, and passing the combined streams upwardly into one of the delayed coking drums.

S. Process according to claim 4 wherein said gas oil 14 used to supply heat required to effect the coking is comprised of at least a portion of the hydrogen-enriched second gas oil.

References Cited UNITED STATES PATENTS 1,842,132 1/1932 Trent 208-50 2,727,853 12/1955 Hennig 208-51 3,072,560 1/ 1963 lPaterson et al 208-68 3,117,921 1/1964 Gorin 208-50 3,132,088 5/1964 Beuther et a 208-68 3,172,840 3/1965 Paterson 208-80 3,172,842 3/ 1965 Paterson 208-80 3,193,487 7/ 1965 Beuther et al. 208-68 3,321,395 5/1967 Paterson 208-107 3,338,817 8/1967 Zrinscak et al. 208-46 3,338,818 8/1967 Paterson 208-58 DELBERT E. GANTZ, Primary Examiner V. OKEEFE, Assistant Examiner U.S. Cl. X.R. 208-8, 51,131 

